Dual-axis plane (double girder) - aircraft with a tail, which is set into two beams, generally parallel to the wings. There are a number of reasons for the constructor, influencing the choice of this particular design:
1. Needs to be loaded from the back door like Fairchild C-119 or C-82 Packet.
2. Designing an aircraft with a pushing propeller or jet type with an engine in the rear (tail) part. Examples are De Havilland 100 or Bell XP-52.
3. Ability to fire from the rear hemisphere and improve visibility, like Focke-Wulf 189 Uhu.
4. Optimization of the aerodynamic configuration for aircraft with two in-line Northrop P-61 or Lockheed P-38 Lighting engines.
5. A two-seater aircraft that was designed and built from 2 copies of existing copies, like the Messerschmitt Me 609 or North American F-82 Mustang.
6. Provide additional hanging space for external load in accordance with Scaled Composites WKT.
7. Simultaneous increase in internal volume and structural rigidity, as in the Virgin Atlantic GlobalFlyer or Voyager.
Examples biaxial aircraft: Yak-58, Su-80, Fighter D flying car Terrafugia Transition, M-17, SAAB J21, RQ-7 Shadow, De Havilland 110 Sea Vixen, Adam A500, A700, FMA IA 67 Cordoba, NA OV -10 Bronco, Lockheed P-38 Lightning, Hughes XF-11, Focke-Wulf 189 Uhu.